Gaussmeter project

[-Elepro-]

hello,

here's my project....
range: 1730 north - 1650 south (with allegro A1302 hall sensor)
sensivity calibration (for use other sensor) from 0.250 mV/G to 6 mV/G
peak hold mode
auto zero set
10 bit A/D
programmed IC euro 30 (worldwide shipping included)

video

[-Elepro-]

bye

[salvarsan]

Originally Posted by -Elepro-

here's my project....
range: 1730 north - 1650 south (with allegro A1302 hall sensor)
sensivity calibration (for use other sensor) from 0.250 mV/G to 6 mV/G
hold peak mode
auto zero set
10 bit A/D

Nice execution.

The peak hold mode is an excellent feature.


What sort of battery life do you get?

Using the A1302, the limiting gauss should be +/- 1925G in increments of 4G.

Any idea why that's not happening?

FWIW, I've cobbled up a similar project using an Arduino.
Ideally, we'd have a 12 bit A/D for this one.

-drh

[-Elepro-]

Originally Posted by salvarsan

Nice execution.

The peak hold mode is an excellent feature.

thanks

What sort of battery life do you get?


with my display (white character does not allow backlight off) current consumption is 16mA with dimmer and 20mA with full light.... if you use a display with black character you can switch off backlight... alkaline 9v battery is 500mAh and more.....


Using the A1302, the limiting gauss should be +/- 1925G



read well datasheet vout is min 0,25 and max 4,7 ..... my gaussmeter has 5% and 93% limits.... out of these limits display shown "out of range"
with ad22151 limits should be +/-5000 gauss but with worse resolution


in increments of 4G.

my firmware has a "kind of oversample"- for every value displaied there are 1024 sample in normal mode and 64 in peak hold mode.... then... watch this video (excuse out of focus)...display shown 0-1-2-3-4-5-6 gauss

excuse for my bad english

[-Elepro-]

Originally Posted by salvarsan

Ideally, we'd have a 12 bit A/D for this one.

-drh

i see now arduino boards.... all have 10 bit ADC

[-Elepro-]

a clarification for who contact me with PM


i don't sell kit because i have not way to make it...
i sell only the programmed integrated circuit with my software on it...

all other parts are available everywhere for about 15 euro (lcd included)...
....pcb is so simple that it is possible to build with a pcb pen (i can explain how) or with press-n-peel technique


bye

[MKB]

Excellent looking project, PIC's are amazing versatile devices. However, if you ever issue a revision, I'd suggest replacing the 7805 with a stepdown switching regulator, or use four cells with the circuit. You're losing a lot of 9V battery life to heat with the 7805.

Do you have a method of performing an absolute calibration of the meter? Is there a standard calibration magnet available? Or is the hall effect sold as a pre-calibrated part? I built a gaussmeter using a Melexis linear hall effect and a panel meter, and it works well, but do not know if it is anywhere near calibrated or not.

[Joe Gwinn]

Originally Posted by -Elepro-

a clarification for who contact me with PM


i don't sell kit because i have not way to make it...
i sell only the programmed integrated circuit with my software on it...

all other parts are available everywhere for about 15 euro
....pcb is so simple that it is possible to build with a pcb pen (i can explain how) or with press-n-peel technique

You will sell far more units if you put complete kits together.

It's a real nuisance and expense for your customers to buy one of this and one of that, while you can buy 50 of this and 50 of that and assemble the kits for very little per part. As for the PCB, again making one is a big nuisance for your customers. There are multiple companies in the US that will make good PCBs in small quantities for you, and if you order 50 it gets pretty cheap. Given that you price in Euros, I assume you are in Europe. I would assume that there are PCB houses in Europe as well. In the US, the board houses advertise in the back pages of electrical engineering trade magazines like EDN and EET as providing prototype boards.

There are lots of one-man shops developing and selling kits for various purposes, so there must be reasonable money in it.

[-Elepro-]

Originally Posted by MKB

I'd suggest replacing the 7805 with a stepdown switching regulator,

current consumption (especially witout lcd backlight) is very low.... power dissipation too
7805 is inexpensive and has noise and ripple free output.... important for adc and sensor supply

Do you have a method of performing an absolute calibration of the meter? Is there a standard calibration magnet available?

i do not sell meter ..... who build my meter can performing perfect calibration comparing it with another meter or a reference magnet or can Put their trust in sensor quality

Or is the hall effect sold as a pre-calibrated part?

allegro a1302 is uncalibrated.... but with my meter you can use any other sensor (sensivity from 0.250 to 6 mv/gauss) you must only set it in calibration menu


I built a gaussmeter using a Melexis linear hall effect and a panel meter, and it works well, but do not know if it is anywhere near calibrated or not.

melexis produce a very cool sensor mlx90215... but they do not issue programming specs and i won't buy their programmer.... other their sensor i think are uncalibrated....

bye

[-Elepro-]

Originally Posted by Joe Gwinn

You will sell far more units if you put complete kits together.

It's a real nuisance and expense for your customers to buy one of this and one of that, while you can buy 50 of this and 50 of that and assemble the kits for very little per part. As for the PCB, again making one is a big nuisance for your customers. There are multiple companies in the US that will make good PCBs in small quantities for you, and if you order 50 it gets pretty cheap. Given that you price in Euros, I assume you are in Europe. I would assume that there are PCB houses in Europe as well. In the US, the board houses advertise in the back pages of electrical engineering trade magazines like EDN and EET as providing prototype boards.

There are lots of one-man shops developing and selling kits for various purposes, so there must be reasonable money in it.

hi Joe,

you are right but i can't at this moment... but if anyone would do this i can offer programmed microcontrollers with a good discount rate

for the moment as required by PM in my next post i'll give a detailed parts list and info on the pcb build....

bye

[-Elepro-]

here's list....


R1 - 10 kohm trimmer
R2 - 5.6Kohm 1/4 watt
R3 - 47ohm 1/4 watt (you can increase this value for decrease backlight intensity and have a more long life battery)
R4- 1Kohm 1/4 watt (this is for backlight dimmer)

C1 - 330nF polyester
C2 - 100nF polyester
C3 - 100nF polyester
C4 - 100nF polyester (this is in the probe near sensor... watch photo...)

D1 - 1N4001 (or 02 03 04 05 06 07... is only for polarity inversion protection)

IC1 - 7805T (5 volt voltage regulator)
IC2 - A1302 (hall sensor)
IC3 - PIC16F883 (microcontroller...... needs my software on it)

1 X HD44780 compatible 16X2 (16 character X 2 row) lcd display (with positive voltage contrast)

2 X - normally open push button
2 X - SPST switch
1 X - DIL28 narrow socket (for IC3)

1 X 9volt battery clip

conn 1-2-3-4-6 - any 90° 2.54mm pitch connector (or you can solder wire directly in the pcb )
conn5 - you can realize it with pin header (soldered to display) and 1/2 DIL32 ic sochet (soldered to pcb)


________________________________________________________ _______

about trimmer and capacitor dimension, it would be better to realize first pcb so you can try them on it (anyway all have 5.08mm pitch)
trimmer must have regolation on bottom too (the pcb have a hole under it.... trimmer must be set from rear of the pcb because on top will be display.... watch pcb render image)

about display, i buoght this .... but you can buy any other similar hd44780 16X2 compatible with same dimension and positive voltage contrast (you can ask me)
if you buy display with black characters ( black on green) you will can turn off backlight (then circuit does not required R4 1Kohm dimmer resistor).... instead display with white character always needs backlight (and you have make dimmer with R4 1K resistor)

my suggestion is to try to realize pcb first....
in my next post i explain two simple way

bye

[-Elepro-]

here's pdf for pcb.... print it with 100% dimensions!!!!

expert can make pcb with photo_etching technique or cnc milling (i can issue gcode for this )

all can make pcb easily using these method:

- press-n-peel method - i don't explain.... you can search on youtube or google... link


otherwise you can obtain pcb following next steps (it will not wonderful but.... )

- print pdf and cut a board image (photo-etching image)
- attach it on copper clad board with double-sided tape
- make holes (don't forget mounting screw holes and trimmer regolation hole)
- remove paper
- with great pacience copy trace (with the help of holes) with a permanent pen
- put board in ferric chloride
- clean trace with thinner


bye

[firewire]

Thanks, -Elepro-
Now that's pretty cool!!!
Anyone up for making a mouser parts list?
Then we all can kinda order are own kit!!!

[firewire]

Here is what I have so far. After the = is Mouser part #.
I could not find 330nF E-Bay -
The DIL28 (for ic3) but could if your good! go with out the socket solder directly to the board?

R1 - 10 kohm trimmer = 858-38PKABR10KLF30
R2 - 5.6Kohm 1/4 watt = 291-5.6K-RC
R3 - 47ohm 1/4 watt = 291-47-RC
R4- 1Kohm 1/4 watt = 291-1K-RC

C1 - 330nF polyester = 594-2222-367-12334 NON in stock.
C2 - 100nF polyester = 594-222236525104
C3 - 100nF polyester = 594-222236525104
C4 - 100nF polyester = 594-222236525104

D1 - 1N4001 = 625-1N4001-E3/54

IC1 - 7805T = 512-KA78T05TU
IC2 - A1302 = 621-AH337-PL-A
IC3 - PIC16F883 (microcontroller...... needs my software on it)

1 X HD44780 compatible 16X2 = 696-LCM-S01602DSRA (Think this will work?)

2 X - normally open push button = 633-SB4011NOH-RO
2 X - SPST switch = 1055-TA2120-EVX
1 X - DIL28 narrow socket (for IC3) =????=Socket for IC2

1 X 9volt battery clip

Anyone like to double check my parts!?!?!?!?

Thanks,

[-Elepro-]

trimmer is too big....

never solder microcontroller

hall sensor in your list is a switch .... the only one linear hall sensor they have has 2,5mV/G.... then you could measure max about +/- 800 gauss ....

c4 is better small because must fit in the probe

here's my list.... it is not complete and checked yet....

http://www.mouser.com/ProjectManager...sID=2c947e7457

[-Elepro-]

edit: list in link is wrong.... watch next post


ok, now list is complete.... there are not only connectors.... (here is for display)
display has black character so it's possible use it without backlight....
backlight has more current consumption than mine so i suggestion to change backlight switch with a push button..... (there are 3 button in list and 1 toggle switch for on/off)
R3 for this display is 15 ohm and trimmer R1 10k - 20k .... in list here's a 20kohm

hall sensor in list allow measure of about +/- 800 gauss (mouser has only this) then remove it if you want measure alnico and buy an A1302 on ebay.....

tomorrow i'll check list again

bye

[firewire]

Cool!!!
That's good to know on the Hall sensor A1302 is the way to go!
Now all that would be need is a link to get you programed chip!!

[-Elepro-]

wait... i found correct display with low power backlight
but.... do not order yet!

[-Elepro-]

ok, this is definitive list


R1 - 10 kohm trimmer ---mouser has only one 20k of right dimensions...but it's ok 652-3318S-1-203

R2 - 5.6Kohm 1/4 watt 660-CF1/4C562J

R3 - 47ohm 1/4 watt (you can increase this value for decrease backlight intensity and have a more long life battery) 660-CF1/4CT52R470J

R4- 1Kohm 1/4 watt (this is for backlight dimmer) ---- not useful for display in this list

C1 - 330nF polyester ------ 505-MKS20.33/63/5
C2 - 100nF polyester ------- 505-MKS2.1/63/5T
C3 - 100nF polyester --------- 505-MKS2.1/63/5T
C4 - 100nF polyester (this is in the probe near sensor... watch photo...) ------- 505-MKS02.1/63/10

D1 - 1N4001 (or 02 03 04 05 06 07... is only for polarity inversion protection) ----- 625-1N4001-E3/54

IC1 - 7805T (5 volt voltage regulator) ----- 863-MC7805BTG
IC2 - A1302 (hall sensor) ----- mouser has only this but can measure +/-800 gauss..... not good for alnico ----- 828-OHS3150U
IC3 - PIC16F883 (microcontroller...... needs my software on it)---- contact me

1 X HD44780 compatible 16X2 (16 character X 2 row) lcd display (with positive voltage contrast) -----key in NHD-0216K1Z-FS select low power backlight and then choose color

2 X - normally open push button ------- 506-MSPS103C0
2 X - SPST switch ----------- 1055-TA2120-EVX
1 X - DIL28 narrow socket (for IC3) -------- 517-4814-3004-CP

1 X 9volt battery clip ------ 534-84-6

conn 1-2-3-4-6 - any 90° 2.54mm pitch connector (or you can solder wire directly in the pcb )

conn5 - ------ 517-929834-01-16 with 517-974-01-16

bye

[mickmutante]

How can I get the IC3-PIC16F883 with the program.?

[-Elepro-]

you have a private message....

[-Elepro-]

for who needs sensor

A1302 link

AD22151 link

[RedHouse]

Originally Posted by mickmutante

How can I get the IC3-PIC16F883 with the program.?

Elepro, I'd like to know your details also, please PM me?

..
...
....

Just out of curiosity, how many folks here would get a kit if I put together a group-buy scenario? if there is enough interest I will work out the details and prices after I get a response from Elepro.

[JasonG]

This looks like a great project but, being new the pickup winding I wonder how it compares with other units.

[salvarsan]

Originally Posted by JasonG

This looks like a great project but, being new the pickup winding I wonder how it compares with other units.

Sorta like, if you buy a commercial gaussmeter, it costs between 250 and 1000 USD and is overkill for pickup builders.


If you build Elepro's kit, you can probably keep the price under 100 USD and have something specifically intended for pickup builders.



-drh

[David Schwab]

Originally Posted by RedHouse

Just out of curiosity, how many folks here would get a kit if I put together a group-buy scenario? if there is enough interest I will work out the details and prices after I get a response from Elepro.

Count me in.

[JasonG]

I would go for a group buy too. The lay out is so simple you might be able to get away with using vero board. I would not need the board but if it worked best for everyone to have a complete kit , I would buy a full kit.

[RedHouse]

The Who's-In on the Group Buy List:
Redhouse
David Schwab
JasonG

Ok so that makes three (3), anyone else?.

I will be start a new thread for posts regarding the group buy

[salvarsan]

Are the gaussmeter board layout files available?
We can have circuit boards professionally made from board files.


-drh

[JasonG]

You might want to post stuff like this on the group buy post.
My guess is that there are plenty of guys around here who could cook up a board for you. Unless someone can make those boards at that level cheap I would think few people would find in advantages to make the board part of the kit. If we got a lot more people in on this the price per board would drop and it might be better to add it to the kit. But we will have to see what happens.

[RedHouse]

Originally Posted by JasonG

You might want to post stuff like this on the group buy post.
My guess is that there are plenty of guys around here who could cook up a board for you. Unless someone can make those boards at that level cheap I would think few people would find in advantages to make the board part of the kit. If we got a lot more people in on this the price per board would drop and it might be better to add it to the kit. But we will have to see what happens.

Yes please do post in the group-buy thread just to keep it all together.

If one wants to have a PCB board done by a circuit board mfr that's ok with me. Unsually it's not cheap until you make more than 20 or so boards, and even then the first round is always more expensive because they (usually insist) on doing a "set up" which implies a fee. Doing only 10 or 15 boards usually doesn't drive the cost down with a PCB house.

When I volunteered to do a PCB for this project, I was speaking of ones I make myself, I wasn't speaking of getting a PCB house to do a run.
If you look on my website you can see examples of boards I make and have made, here are some links:

ClassicAmplification.com :: Classic'Vibe
The ForumVibe Project - Page 2: "Making a PCB"
ClassicAmplification.com :: Audio Projects

My boards are very high quality (though my pictures suck), and I was intending to do them ...(just this one time)... at a bargain price for the forum members to help this project fly.

I'm thinking $10/ea would be very fair and keep the total cost of the project down. Classic Amplification (my business) charges $25 minimum per board cut-n-drilled (a bare board w/o any components) when I manufacture boards for clients. In case anyone's wondering, it takes about an hour and a half to make a board from start to finish just to give some perspective in case anyone thinks I'm trying to take advantage.

Anyway, we should be posting this stuff over in the group-buy thread just to keep it all together.

[Arndawg56]

I am new to this forum, I joined to get in on the "group buy". I used to just read and learn from here, but this is something I can't pass up. I am also the guy in the photo on the "ClassicAmplification.com :: Audio Projects" web page. I own that very expensive mixing desk that brad made the 32 PCB's (and mic pre's). Not only did the boards look great, but every one of them works perfectly.

If your going to make the boards, Red House, I want one.

[RedHouse]

(Weird, I posted this a few minutes ago and it didn't get onto the forum)

Elepro,

Could you post some words here on building the gauss meter? I'm sure we're going to need it.

There are already pictures and a link to the video, but we should have some instructions posted too. (the do's-n-don'ts)

Please post a few words on these topics:

1.) any additional info that might be needed to build or use the meter
2.) how to set the trimmer for optimal use
3.) how to operate the unit, CALIBRATION, switch functions etc.
4.) how to troubleshoot it if a problem arises during construction or during use.
5.) list any "Do NOT" things that might cause the meter to fail

[David King]

I wouldn't mind being in on the group buy but also have the capability to create my own pcb the old fashioned way and probably have all the passive components in my collection. I think we'd need at least 10 folks to make it worthwhile and then the savings would be mostly in time.. I'll check out the other thread.

[RedHouse]

Originally Posted by David King

I wouldn't mind being in on the group buy but also have the capability to create my own pcb the old fashioned way and probably have all the passive components in my collection. I think we'd need at least 10 folks to make it worthwhile and then the savings would be mostly in time.. I'll check out the other thread.

David, please don't post here about being in on the group buy, there is another thread here: Gaussmeter Kit Group-Buy

It's better to let this thread be about the meter and it's details, and let the other thread be about the group-buy of components.